package com.ym.game.utils;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.UnsupportedEncodingException;
import java.net.URLEncoder;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Map;

public   class  MD5Util {
    /**
     * 默认的密码字符串组合，用来将字节转换成 16 进制表示的字符,apache校验下载的文件的正确性用的就是默认的这个组合
     */
    protected   static   char  hexDigits[] = {  '0' ,  '1' ,  '2' ,  '3' ,  '4' ,  '5' ,  '6' ,
            '7' ,  '8' ,  '9' ,  'a' ,  'b' ,  'c' ,  'd' ,  'e' ,  'f'  };  

    protected   static  MessageDigest messagedigest =  null ;
    static  {
        try  {
            messagedigest = MessageDigest.getInstance("MD5" );
        } catch  (NoSuchAlgorithmException nsaex) {
            System.err.println(MD5Util.class .getName()
                    + "初始化失败，MessageDigest不支持MD5Util。" );
            nsaex.printStackTrace();
        }
    }

    /**
     * 生成字符串的md5校验值
     *
     * @param s
     * @return
     */
    public   static  String getMD5String(String s) {
        return  getMD5String(s.getBytes());
    }

    /**
     * 判断字符串的md5校验码是否与一个已知的md5码相匹配
     *
     * @param password 要校验的字符串
     * @param md5PwdStr 已知的md5校验码
     * @return
     */
    public   static   boolean  checkPassword(String password, String md5PwdStr) {
        String s = getMD5String(password);
        return  s.equals(md5PwdStr);
    }

    /**
     * 生成文件的md5校验值
     *
     * @param file
     * @return
     * @throws IOException
     */
    public   static  String getFileMD5String(File file)  throws  IOException {
        InputStream fis;
        fis = new  FileInputStream(file);
        if(fis.available() == 0)
        {
        	 fis.close();
        	 return "";
        }

        byte [] buffer =  new   byte [ 1024 ];
        int  numRead =  0 ;
        while  ((numRead = fis.read(buffer)) >  0 ) {
            messagedigest.update(buffer, 0 , numRead);
        }
        fis.close();
        return  bufferToHex(messagedigest.digest());
    }

    public   static  String getMD5String( byte [] bytes) {
        messagedigest.update(bytes);
        return  bufferToHex(messagedigest.digest());
    }

    private   static  String bufferToHex( byte  bytes[]) {
        return  bufferToHex(bytes,  0 , bytes.length);
    }

    private   static  String bufferToHex( byte  bytes[],  int  m,  int  n) {
        StringBuffer stringbuffer = new  StringBuffer( 2  * n);
        int  k = m + n;
        for  ( int  l = m; l < k; l++) {
            appendHexPair(bytes[l], stringbuffer);
        }
        return  stringbuffer.toString();
    }

    private   static   void  appendHexPair( byte  bt, StringBuffer stringbuffer) {
        char  c0 = hexDigits[(bt &  0xf0 ) >>  4 ]; // 取字节中高 4 位的数字转换, >>> 为逻辑右移，将符号位一起右移,此处未发现两种符号有何不同
        char  c1 = hexDigits[bt &  0xf ]; // 取字节中低 4 位的数字转换
        stringbuffer.append(c0);
        stringbuffer.append(c1);
    }

}
